1. Field of the Invention
The present invention relates to a stringer tape having a beaded edge along its one longitudinal edge, the beaded edge including a tube integrally formed along the longitudinal edge of the stringer tape and a filler thread or filler threads inserted through the tube, and also relates to a slide fastener including a pair of such stringer tapes and two rows of coupling elements extrusion-molded from plastic and sewn to the respective longitudinal edges of the stringer tapes.
2. Description of the Prior Art
Heretofore, it has been commonly known in this field that, in order to provide a longitudinal beaded edge on the stringer tape, intertwined yarns are sewn to, woven into or knitted into a longitudinal edge of the stringer tape.
A typical stringer tape of the type described is disclosed in Japanese Utility Model Publication No. 59-25215. In this conventional stringer tape, a longitudinal beaded edge is provided in the following way; first, a reinforcing filler comprised of an elongated central core and a warp-knit tube surrounding the elongated central core and extending longitudinally therewith is provided. The warp-knit tube has on its periphery a plurality of longitudinal wales. Secondly, such a reinforcing filler is inserted through a woven tube formed along one longitudinal edge of the stringer tape. Thirdly, the woven tube is heat-set and thus shrunk to clench the inside warp-knit tube therein.
Furthermore, Japanese Utility Model Publication No. 63-30245 discloses a slide fastener comprising a pair of stringer tapes and two coupling element rows mounted on the opposed inner longitudinal edges of the stringer tapes. The coupling element rows are made from plastics through an extrusion-molding process. Each element row is folded back on itself to provide a U-shape to cause each element to have opposed upper and lower legs. Every second element is connected by an integral connecting portions alternately at the upper leg and the lower leg. In addition to being integrally connected, the coupling elements are connected together with connecting rods embedded in the upper and lower legs. Then, the U-shaped element row is clamped to the longitudinal edge of the relevant stringer tape. Eventually, the U-shaped element row is sewn to the stinger tape.
The stringer tape according to the first-mentioned Japanese Utility Model Publication suffers from drawbacks. Since the woven tube is heat-set and thus shrunk to clench the inside warp-knit tube therein, the longitudinal beaded edge is made too rigid, thus lacking in resiliency and flexibility. Furthermore, for the same reason, the rigid beaded edge is disinclined to be pierced by sewing needles so that, although this stringer tape lends itself to metal coupling elements which are mechanically clamped to the longitudinal edge of the stinger tape, it is extremely difficult if not completely impossible to sew discrete plastic coupling elements to this stringer tape. Furthermore, even if this stringer tape is used on metal coupling elements, it still has a disadvantage in that, since the U-shaped coupling elements are clamped to the thick and rigid beaded edges, which will be less likely to squeeze, the slide fastener as a whole is made considerably thick, which goes against the recent fashion in this field wherein a thinner slide fastener has been sought.
The slide fastener according to the second-mentioned Japanese Utility Model Publication also suffers from drawbacks. Every second element is integrally connected to each other by the connection portion alternately at the upper leg and the lower leg. In addition to being integrally connected, the individual elements are connected together with connecting rods embedded in the upper and lower legs. As a result, the coupling element row is stiff, so that the slide fastener as a whole lacks in flexibility.
Furthermore, the stringer tape has no beaded edge along an inner longitudinal edge, therefore being flat, so that the coupling element row mounted to the flat longitudinal edge is liable to become detached or displaced from the flat longitudinal edge of the stringer tape. For the same reason, it is quite difficult to firmly mount a separating device to the lower end of the opposed longitudinal edges.